Process of bleaching sized cotton fabrics



8 1 8 9 s R RQQW April 17, 1962 J. LINDSAY 3,030,171

PROCESS OF BLEACI-IING SIZED COTTON FABRICS Filed April 1'7,v 1959 2Sheets-Sheet 1 i BY I I INVENTOR.

Josaw/ Z/IVDSAY LD April 17, 1962 J. LINDSAY 3,030,171

PROCESS OF BLEACHING SIZED COTTON FABRICS Filed April 1'7. 1959 2Sheets-Sheet 2 COTTON CLOTH Aqueous Bath 60 to 200 F Ph I0 120 M- COTTONCLOTH Nuocl impregnated Sueeze| 1:050 to I507; saturation STEAM IElevated. temperaturfi l5 min. to 4hrs.

ash O g 65 to 200 F COTTON CLOTH Substantially Free of NaOC l immerse inboth Aqueous Bath 40 to 160 F -Below 2% by Wt.

5 fnB to 150% Satumtion STEAM Elevated temperature -l5 min to 3 hrs.

JNVENTOR.

ana/w I 101/054) BLEACHED COTTON CLOTH United States Patent 3,030,171PROCESS OF BLEACHING SIZED COTTON FABRICS Joseph Lindsay, Clemson, S.C.,assignor, by mesne assignments, to Pittsburgh Plate Glass Company FiledApr. 17, 1959, Ser. No. 807,186 18 Claims. (Cl. 8-109) The presentinvention is concerned with bleaching of woven or knitted cellulosic andlike vegetable fabrics, especially cotton fabrics. Still moreparticularly, the present invention relates to the bleacing of sizedfabrics of this character and in particular the sized cotton fabric.

In the bleaching of textile fabrics, many different processes have beenemployed. Among the more common bleaching processes are those involvingthe use of alkali metal hypochlorite solutions and aqueous hydrogenperoxide solutions or combinations of both. While these processes haveproved effective in many applications, quite frequently, disadvantagesor deleterious effects arise which render them unacceptable. Thus, insome cases while the strength of the fabric is not affected by thebleaching operation conducted, some sacrifice in the whiteness of thematerial treated is necessitated. In other cases good whiteness isachieved at the expense of a reduction in the strength of the fiberscontained in the fabric treated. A further disadvantage of many of thechemical bleaching treatments heretofore undertaken is the substantialcosts of the chemicals involved.

According to the present invention, a novel process has been providedfor bleaching woven or knitted cotton and like fabrics, especiallycotton fabric which has been sized, (that is impregnated with variousstarch materials well-known in the art) which effectively solves many ofthe problems now encountered in bleaching such cloth. Thus, employingthe novel sequence of steps hereinafter set forth, a bleaching processis provided which produces a plurality of beneficial effects inbleaching these cotton fabrics. Cotton fabrics as used herein in thespecification and claims are intended to include those fabrics which arecomposed essentially entirely of cotton fibers as well as fabrics whichare mixtures of cotton fibers with other fibers such as wool, rayon,nylon, and other synthetic and natural fibrous materials easily blendedwith cotton fibers. Cotton unions as contemplated generally contain atleast 15 percent by weight of cotton therein. The fabrics include clothwhich has been woven, as well as knitted cloth.

Thus, following the teachings of this invention cotton fabrics arebleached to a high degree of brightness while at the same time fibrousstrength in the fabric bleached is substantially unaffected.

Quite frequently, it is also found that many conventional desizingoperations may be eliminated entirely without deleterious effect uponthe bleaching steps so that sized fabrics treated in the novel processherein disclosed not only are desized during the operation, but arebleached to an exceptionally high degree. A further advantage of theprocess described herein is that it is easily adapted to someconventional bleaching equipment, thus providing an improved bleachingprocess with little or no equipment changes. A further advantage of theprocess involves a considerable reduction in the quantities of bleachingchemicals employed, thereby reducing the costs of a given bleachingoperation.

In accordance with this invention, a sized woven or knitted vegetablefabric such as cotton is introduced, without desizing, into an aqueoussolution of an alkali metal hydroxide and an alkali metal hypochloriteand/ or an alkaline earth metal hypochlorite. Sodium, potassium andcalcium hypochlorite are typical of the hypochlorites 3,030,171 PatentedApr. 17, 1962 employed. The fabric is permitted to remain in thesolution for a period of time sufficient to substantially impregnate thefabric with the solution. After nipping to give 50 to percent liquorpickup basis the weight of the dry goods, the goods are heated in steamfor a period of time suflicient to disperse the motes and render thenon-fibrous content of the fabric water extractable. Thus, starches aresolubilized and oils and fats emulsified during the steaming operation.Fibers in the fabric treated swell and softening and dispersion of themotes occurs. In addition, the hypochlorite content of the solutionimpregnated fabric is substantially removed.

The material after the heating operation is water washed and introducedinto an aqueous solution of hydrogen peroxide. The fabric is permittedto remain in the hydrogen peroxide solution for a period of timesuflicient to impregnate substantially the woven fabric with thehydrogen peroxide solution. After the fabric has been impregnated to 50to 150 percent of liquor on weight of dry goods, Illa-1S then heated aperiod of time sufficient to bleach it to the required degree.

In the treatment of extremely heavy fabric such as cotton poplins andthe like, a desizing step may conveniently be employed to insureadequate bleaching of the material. Thus, in bleaching a material ofthis type, the fabric is desized in a conventional enzyme desizingsolution and then subsequently introduced into an aqueous solution of analkali metal hydroxide and a hypochlorite of the group consisting ofalkali metal hypochlorites and alkaline earth metal hpochlorites in thefashion as herein above described.

For a more complete understanding of the present invention, reference ismade to the accompanying drawing in which FIG. 1 is a diagrammaticillustration of the method and apparatus utilized in bleaching wovenvegetable fabrics according to this invention and FIG. 2 is a flow sheetof the method.

In the drawing is shown the fabric 1, filameburners 2 and 3, a washingtank 4, the caustic-hypochlorite saturator 10, J-box 17, washer 22,hydrogen peroxide saturator 25, J-box 31, washer 36. In the operation ofthe process in conjunction with the equipment shown in the drawing, awoven fabric is drawn over rollers 5, 6 and 7 so that the fabric isessentialy intermediate between the positioning of burners 2 and 3 andthe flames produced by these burners. Passage of the cloth intermediatethe burners effectively singes lint, fuzz and other like material fromthe cloth surface. The fabric is then drawn through washer 4 and, afterwashing or quenching, is delivered by way of rollers 8 and 9 to causticsaturator 10. In saturator 10 the fabric is contacted with an aqueousalkali metal hydroxide solution containing an alkali metal hypochloriteor an alkaline earth metal hypochlorite. A holdup of cloth in saturator10 is permitted to accomplish a substantial saturation of the materialwith the solution contained therein. Upon leaving saturator 10, thefabric is passed through rollers 13 and 14 and excess solution expressedor squeezed therefrom. The fabric is then passed over roller 15 andintroduced into the J-box 16. Located at a point on the J-box is a steaminlet line 17. Steam is introduced into the J-box at a temperature ofapproximately 212 F. at atmospheric pressure, and the cloth is permittedto remain therein for a substantial period of time.

After the steam treatment, the cloth is drawn over rollers 18, 19, 20,21 and 23 through a washer 22. The cloth is then introduced intosaturator 25 where it is contacted with an aqueous solution of hydrogenperoxide. A holdup of the cloth in saturator 25 is permitted for aperiod of time sufficient to accomplish a substantial saturation of thecloth with the hydrogen peroxide solution. After the cloth has beenthoroughly saturated with the hydrogen peroxide solution contained insaturator 25, it is drawn through rollers 28 and 29 over roller 30 intothe J-box 31. Rollers 28 and 29 function to express excess solution fromthe cloth leaving the saturator 25. Steam is introduced into the J-box31 through a steam inlet 30 at a temperature of approximately 212 F.,and the cloth is permitted to remain therein for a period of timesuflicient to accomplish bleaching of the impregnated cloth. Uponcompletion of the bleaching operation in the J-box 31, the cloth isdrawn over rollers 33, 34, 35, 37, 38 and 39 through a washer 36 whereit is thoroughly washed with water and removed from the tank for furtherprocessing, for example, dyeing operations or merely to be dried andutilized as such.

The singeing of the cloth is accomplished by recourse to ordinaryflame-burners. The cloth is positioned between the burners so that it isessentially equidistant from the flames issuing from both burners, and auniform distribution of the flame to both sides of the fabric traversingthe flame area takes place. At this point in the operation, the cloth ispassed through at a relatively rapid rate so that scorching or burningdoes not take place. Usually a travel speed of 150 yards of cloth perminute is sufficient to successfully permit a singeing of the clothwithout producing any deleterious effects thereon. The singeingoperation is conducted on the woven fabric to remove hair, lint andmaterials of this nature which adhere to the surface of the cloth.

' All of the Washers conveniently employ tap water maintained at roomtemperatures, that is, 65 to 80 F.; however, hot water may be used wheredesired or needed. Thus, water temperature of 100 to 200 F. may beemployed. If desired, the washers may be equipped with heaters tofacilitate maintenance of elevated temperatures.

The composition of the alkaline solution of the alkali metal or alkalineearth metal hypochlorite utilized in accordance with this invention isimportant for the accomplishment of the results desired. Thus, thehypochorite concentration in the aqueous alkaline solution is controlledso that there is provided in this solution between 03 to 5 grams activechlorine per liter of solution. Preferably the hypochloriteconcentration is so maintained that there is provided between 1 and 3grams active chlorine per liter of solution. The solution is maintainedin the alkaline state and within a definite alkaline range (i.e. above7). The pH of the solution is usually maintained between 10 and 14preferably in the 12 to 13 range on the pH scale.

While in the accompanying drawing sodium hydroxide is utilized as thealkaline medium, it is of course understood that other alkali metalhydroxides may be employed such as potassium hydroxide. Generallyspeaking alkali metal hydroxide concentrations are adjusted such thatthe fabric leaving the saturator contains between 2 and 5 percent byweight of the free alkali metal hydroxide on weight of dry goods.Preferably alkali metal hydroxide concentration is on the order of 3percent by weight basis the weight of the dry goods.

The fabric treated in the aqueous alkaline solution is maintained sothat essentially complete saturation of the cloth occurs. This may beaccomplished by adjusting the nip roll pressures such that an adequatepickup within the caustic saturator is accomplished. Cloth which picksup solution in the saturator on the order of 50 to 150 percent by weightbasis the weight of the dry fabric is considered sufliciently saturatedwith solution for the purposes of this invention.

Temperature conditions within the caustic saturator are considerablyvariable and generally ranging between 60 and 200 F. Preferablytemperatures are maintained so that the solution temperatures rangebetween 100 and 140 F. Operation in the preferable range produces themost satisfactory results.

Rollers 13 and 14 as described in the above drawing are so positionedthat a squeezing of the cloth is accomplished as it passes between thetwo rolls, and the rolls are adjusted so that the cloth in passingthrough the two rolls has its solution content substantially reduced.Thus, it is preferable in removing cloth from the caustic-hypochloritesaturator for passage to the first steaming operation in the first J-boxthat it be passed through these rolls and pressure applied that thesolution content of the cloth is reduced to between 50 and percent byweight basis the weight of the dry fabric.

In treating cloth in the caustic-hypochlorite saturator as herein abovedescribed, the most beneficial use of the chemicals involved is therebyattained. The main function of the solution contained in the saturatoris to supply adequate chemicals to the cloth to accomplish dispersion ofmotes, seeds and shives contained in the cloth and thereby prepare itfor subsequent bleaching. Little or no bleaching effect is accomplishedby the hypochlorite content of this solution.

In introducing the material to the J-box or steam chest, it is essentialthat certain conditions be observed for maximum effect in the overallbleaching operation in accordance with the present invention. Thus,cloth fed to the steaming chest or zone is permitted to remain thereinduring the steaming operation for a considerable period of time.Generally the time is so regulated that the cloth is maintained withinthis zone for a sufficient interval of time to provide for essentiallycomplete removal of the hypochlorite content of the cloth. In additionto the removal of hypochlorite contained within the cloth or fabric fedto the zone, hydrolysis of starchy materials contained in the clothsizing is accomplished thereby rendering them soluble in the subsequentwashing operations. Maximum dispersion of motes present is alsorealized.

For the successful accomplishment of these results, it is necessary thatelevated temperatures be observed in the operation of this steamingstep. Thus, temperatures should range generally between and 500 F.Preferably steaming is conducted somewhere between about 180 and 220 F.Steaming operations conducted within the above temperature ranges areadequate when the cloth is held in the steaming zone for at least about15 minutes. Generally the cloth is maintained in this zone for between15 minutes to about 4 hours, but conveniently a one-hour treatment isusually suflicient.

Generally speaking, the same considerations are applied to the cloth fedto the hydrogen peroxide saturator as are given to cloth fed to thecaustic saturator with respect to the holdup times employed. Thus, thecloth is usually permitted a holdup in the peroxide saturator sufficientto permit a saturation of the cloth to the degree that a solution pickupof 50 to 150 percent by weight basis the weight of dry fabric isaccomplished. Expression of solution from the cloth as it leaves thetank is accomplished through nip rolls 28 and 29 in the same manner asis accomplished with the cloth leaving the caustic saturator. Thus,cloth as it leaves the hydrogen peroxide saturator has its solutioncontent reduced to between 50 and 150 percent by weight of solutionbasis the weight of the dry fabric.

The hydrogen peroxide concentration is so regulated that the hydrogenperoxide content (anhydrous) thereof is maintained below 2 percent,preferably between about 0.1 to 1 percent by weight hydrogen peroxide(anhydrous) based upon the weight of the solution. Preferably thehydrogen peroxide content of the bath is maintained between 0.3 and 0.7percent by weight based upon the weight of the solution. Thus, as willbe readily seen, bleaching is preferably accomplished in the aqueousperoxide solution with a minimum concentration of peroxide being used.This reduction in required peroxide for a given bleaching operation issubstantial and contributes to a reduction in chemical costs for anygiven bleaching operation. Temperatures in the aqueous hydrogen peroxidebath range generally between 40 and 160 F. preferably between 80 and 155F.

In addition to the hydrogen peroxide content present in the bleachingbath as described above, there is conveniently employed in this aqueoussolution of hydrogen peroxide small quantities of alkali metal silicate.The use of an alkali metal silicate in the hydrogen peroxide bleachingbath enhances the activity of the bleaching agent. Typical of thesilicates contemplated for this use is sodium silicate having thecomposition Na O(SiO where x is a value between 2 and 4. Concentrationsof between 0.1 and 3 percent by weight of solution of 40 Baum sodiumsilicate (Na O(SiO are conveniently employed. Preferably an 0.5 percentby weight concentration is employed.

In connection with both the hydrogen peroxide bleaching bath and thecaustic saturator, recourse may be had to the use of conventionalwetting agents such as aryl sulfonates and other conventional chemicalwetting agents. While these agents may be conveniently employed toinsure adequate pickup of solution by the cloth traversing the bath, itis not essential to the bleaching process that they be employed. Theoperation of both the caustic saturator and the aqueous hydrogenperoxide solution during a bleaching operation with adequate pickup ofsolution has been accomplished without the utilization of wettingagents. The desirability or advisability of using these agents will forthe most part be determined by the character of the cloth employed andits capability of picking up solution readily due to the physicalconstruction of the fabric with respect to the type of fibers employedand the tightness or looseness of the weave.

Cloth, after passing through the aqueous hydrogen peroxide bleachingbath, is stored in a J-box or steam chest. Conveniently a J-box isemployed for this purpose. Holdup of cloth in the steaming area is suchthat it is subjected to the steam at elevated temperature for at least15 minutes. Preferably steaming is conducted for between 30 minutes toan hour, though generally it may range anywhere between 15 minutes and 2to 3 hours. The general guide determining the length of time that thehydrogen peroxide impregnated cloth is subjected to a steaming orheating operation is the accomplishment of complete bleaching by thehydrogen peroxide contained within the cloth. This may be easilydetermined for particular types and weaves of fabric so that a minimumholdup of cloth in the steaming zone for any particular fabric isachieved.

In the operation of the caustic-hypochlorite saturator, it is alsodesirable to employ therein an alkali metal silicate to enhance theactivity of the hypochlorite treatment occurring therein. Generallysodium silicate is employed as the preferred alkali metal silicate inthis bath and amounts ranging between 0.1 to 3 percent silicate may beadded. Conveniently, an 0.5 percent solution of 40 Baum sodium silicateis employed.

When a sized cotton fabric, i.e., a fabric sized with starch, isbleached in accordance with the teachings of this invention, it is foundthat acceptable degrees of brightness are attained. Fiber strengthremains substan tially unaffected and, in some cases, is improved uponover conventional bleaching operations. A sized fabric passing throughthe bleaching operation usually contains in the neighborhood of 9percent starch by weight basis the weight of the fabric. In treatingsuch material without the use of a desizing bath utilizing the causticsaturator and the hydrogen peroxide bleaching bath of the presentinvention, a starch content of one percent or less is usually found inthe treated fabric upon completion of the bleaching cycle. In some casesit is possible to reduce this starch content even further, depending onthe severity of conditions employed in the steaming steps and theconcentrations of the various bath solutions. Generally, however,operating in the preferred ranges with respect to chemicalconcentrations and steaming temperatures and times a reduction of starchcontent in a woven cotton fabric to a one percent level is satisfactoryfor some commercial purposes.

As previously mentioned, for particularly heavy fabrics, such as poplin,in which some difiiculty may be encountered in removing all of thestarch materials to the desired low levels, recourse may be had to aconventional enzyme desize. These baths generally are aqueous solutionswhich contain various well-known enzymatic materials which eifectivelyaccomplish a desizing of the cloth. When an enzymatic desizing step isemployed in connection with the above described bleaching operation, thesingeing step is usually conducted prior to the desizing operation.Thus, cloth so treated is first singed and then desized with theenzymes. After the desizing step, the cloth is fed to a washer in themanner herein disclosed and then treated with the alkaline solution ofthe alkali metal or alkaline earth metal hypochlorite. All other stepsin the process remain the same as described above. Thus, after thealkaline treatment, a steaming operation is conducted after which thecloth is fed to the hydrogen peroxide bleaching step and a subsequentsteaming operation. As can be readily seen, the process is easilyadaptable to any bleaching operation of a cotton fabric irrespective ofthe type or weave.

For a more complete understanding of the present invention, thefollowing examples are given as illustrative of some methods which maybe employed in conducting the present invention and the advantages to beobtained thereby.

EXAMPLE I Three samples of cloth, one a print cloth, one a sateen andone a broadcloth, were bleached following the conventional bleachingprocess and compared with results obtained by following the bleachingprocess as hereinabove described. In the first series of runs, onesample of print cloth, one sample of sateen cloth and a sample ofbroadcloth were passed successively through two caustic saturatorscontaining an aqueous sodium hydroxide solution of 3 percent by weightsodium hydroxide concentration at 140 F. A pickup of about one pound ofsolution per pound of cloth was obtained in the saturators and theweight concentration of the solution in the cloth controlled by nippingto percent by weight of solution basis the weight of the dry cloth as itwas removed from the saturator and placed in the J-box. The samples werepermitted to remain in the J-box for a period of one hour and contactedwith steam at 210 F. (during this time period). The cloth upon removalfrom the J-box was rinsed in water at 210 F. in a two-compartmentwasher.

The samples upon removal from the washing tank were passed into ableaching bath at 122 F. containing one percent hydrogen peroxide byweight and one percent sodium silicate (Na O(SiO by weight. A pickup ofabout one pound of solution per pound of cloth was obtained and thesolution expressed from the cloth as it was removed from the box toprovide a solution content of 100 percent by weight basis the weight ofthe dry cloth. Each of the samples were then placed in another J-boxoperated at 210 F. for one hour and steamed therein. After the one-hourperiod, the samples were removed from the compartments, and washed inwater at 210 F. A series of tests were then conducted on the samples todetermine reflectance, tensile strength and absorbency. The results ofthese tests are shown in Table I.

EXAMPLE II Samples of the same print cloth, broadcloth and sateen astreated in Example I were treated by passing the samples throughsuccessive caustic saturators operated at F. The sodium hydroxideconcentration of the caustic saturators were 3 percent by weight. Inaddition to the caustic concentration, each saturator contained 0.5percent sodium silicate (Na O(SiO by weight and 0.1 percent sodiumhypochlorite by weight. The samples were treated in a J-box for one hourat 210 F. under the same conditions obtained in the treatment of thefirst samples. The hydrogen peroxide bleaching operation was conductedin a hydrogen peroxide bleaching bath at 122 F. containing 0.67 percentby weight hydrogen peroxide and 0.67 percent sodium silicate. The samepickup and expression of solution procedures were followed in Example I,and this set of samples was also treated in a J-box for one hour at 210F. Upon completion of the treatment, the same series of tests were runon these samples as were run on the samples of Example I. The resultsare listed in Table I. These results show that by use of thehypochlorite as disclosed in Example II only two-thirds of the amount ofhydrogen peroxide is required.

Table I Reflect- Tensile Strength ance- Units Absorb- Percent encyrelative (sec.) to MgO Warp, Filling,

lb./sq. in. lb./sq. in.

20 84. 4 22. 7 18.0 2 Example I 21 86.8 55. 3 23. 6 1

22 87. 3 28. 9 16. 6 2. 5 20X 85.0 23. 7 20. 6 2 Example II 21X 85. 758.1 23.0 1 22X 86.0 33. 9 17. 6 2 20D 86. 22. 6 16. 8 2 ExampleIII(a)..-- 21D 87. 4 52. 1 24. 3 1 22D 86. 6 27. 3 18. 9 1 20DX 85. 922.6 18. 4 2 Example III(b).. 21DX 86. 0 53. 6 25. 0 1

All D samples were desized before treatment in the caustic saturator.

All X samples were treated with 0.5 percent silicate in an 0.1 percentsolution of hypochlorite before the peroxide bleaching step.

All #20s are print cloth.

All #21s are sateen cloth.

All #22s are broadcloth.

Reflectance was measured on a Hunter multipurpose reflectometer.Absorbency was measured by dropping water from a pipet held inches fromthe surface of the unstretched cloth. The time required for thedisappearance of the specular reflectance from a drop as visuallyobserved is the absorbency.

EXAMPLE III Two more sets of runs were conducted on desized samples ofcloth of the same types as described in Examples I and II. One set ofruns was conducted with a simple caustic wash at 140 F. while a secondset of runs was conducted in caustic saturators at 140 F. con tainingsodium hypochlorite in 0.1 percent by weight concentration basis theweight of the solution. In addition those runs employing thehypochlorite treatment in the caustic saturator employed 0.67 percenthydrogen peroxide in the bleaching bath at 122 F. while those notemploying the sodium hypochlorite in the caustic solution were treatedwith a one percent by weight aqueous solution of hydrogen peroxide at122 F. The same series of tests as applied to the samples of Examples Iand II were conducted and the results are listed in Table I.

EXAMPLE IV Two more series of runs were conducted on a print cloth and abroadcloth in the same manner described in Example I. All samples,however, were contacted with the caustic saturators at 140 F. whichcontained small quantities of tetrasodium pyrophosphate and oleatesoaps. Thus, samples numbered 23, 23D, 24 and 24D were saturated in 3percent caustic soda while samples 23X, 23DX, 24X and 24DX weresaturated in a caustic soda solution containing 2.5 percent causticsoda, 0.5 percent sodium silicate, 0.1 percent sodium hypochlorite, 0.1percent tetrasodium pyrophosphate and 0.01 percent oleate soap. Allpercentages are by weight of solution. The samples which were passedinto the sodium hypochlorite containing caustic solution were treatedwith an aqueous solution of hydrogen peroxide at 122 F. containing 0.67percent hydrogen peroxide by weight and 0.67 percent sodium silicate byweight. The samples treated with the plain caustic wash were treatedwith a one percent hydrogen peroxide solution containing one percentsodium silicate. All percentages are by Weight of solution. Steamingoperations were conducted as in Example I after the caustic saturationand after the bleaching operation. Rinsing was conducted in the samemanner as set forth in Example I. All samples were tested to determinetheir tensile strength, brightness and absorbency and the results ofthese tests are shown in Table II.

Table II Tensile Breaks Refiect- Absorbency ance (see) Warp FillingEXAMPLE V A series of experiments were conducted on a broadcloth inwhich many variations were employed in the caustic saturator. After thesaturation in the caustic solution, the broadcloth was bleached in threedifferent concentrations of hydrogen peroxide. Caustic saturatorsolutions were at temperatures of 140 F. while peroxide solutions were122 F. Steaming was conducted on the cloth as it was received from thecaustic saturator as well as when it was taken from the hydrogenperoxide bath. The samples are numbered in Table III as 1, 2, 3 and 4and the caustic saturator solution employed on each sample contained thefollowing:

Sample I-3 percent caustic soda.

Sample II3 percent caustic plus 0.1 percent sodium hypochlorite.

Sample III3 percent sodium hydroxide, 0.1 percent sodium hypochloriteand 0.5 percent sodium silicate.

The aqueous hydrogen peroxide bleaching solutions contain, in additionto the hydrogen peroxide, the following components in the followingquantities: 0.55 percent sodium silicate and 0.25 percent sodiumhydroxide. All percentages given above are by weight of solution. Thesamples were tested for reflectance and tensile strength and the resultsare listed in Table III.

Table III Tensile Peroxide Breaks, Reflect- Conc. (by Avg. of armsweight) Warp and illing 1. Conventional:

1.5 22.4 91. 5 1 21. 5 90 0.75 23.2 89 1.5 22.0 93. 5 3. Hypochloriteand Silicate 1 24. 3 92. 5 0.75 24.2 90. 5

As can readily be seen from the examples, operation in accordance withthe teachings of this invention permits the obtention of an adequatebrightness in bleaching operations. Further advantages are obtained inthat considerable reductions in the quantity of hydrogen peroxidebleaching solution necessary to obtain a given quantity of brightnessare easily realized. Good tensile strengths are also obtained.Absorbency values attained are within tolerated While the invention hasbeen described with reference to certain specific examples and drawings,it is, of course, understood that the invention is not intended to belimited thereby since many modifications may be made in the processwithin the skill of the art, and it is not intended that the inventionbe so limited except insofar as appears in the accompanying claims.

I claim:

1. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous alkalinesolution of a hypochlorite for a period of time sufficient tosubstantially impregnate the fabric with solution, removing theimpregnated fabric from solution, heating the impregnated fabric atelevated temperature for a period of time sufficient to disperse themotes and render the non-fibrous content of the fabric water extractableand washing the heated fabric with an aqueous solution.

2. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous alkalinesolution of a hypochlorite, said solution having between 0.3 to aboutgrams active chlorine per liter of solution and containing between 0.1to about 3 percent alkali metal silicate by weight of the solution,maintaining the fabric in contact with the aqueous alkaline solution fora period of time suificient to substantially impregnate the fabric withsolution, removing the impregnated fabric from the solution, heating theimpregnated fabric at elevated temperature for a period of timesuflicient to disperse the motes and render the non-fibrous content ofthe fabric water extractable and washing the heated fabric with anaqueous solution.

3. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous alkalinesolution of a hypochlorite for a period of time sufiicient tosubstantially impregnate the fabric with solution, removing theimpregnated fabric, reducing the solution content of the fabric tobetween about 50 to 150 percent by weight basis the weight of thefabric, heating the fabric in an atmosphere of steam for a period oftime sufficient to disperse the motes and render the non-fibrous contentof the fabric water extractable and washing the heated fabric with anaqueous solution.

4. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the fabric into an aqueous alkaline solution of ahypochlorite, said solution aving between 0.3 to about 5 grams activechlorine per liter of solution and containing between 0.1 and 3 percentalkali metal silicate by weight of solutions, maintaining the fabric incontact with the aqueous solution for a period of time sufficient tosubstantially impregnate the fabric with solution, removing theimpregnated fabric from the solution, reducing the solution content ofthe fabric to between about 50 to 150 percent by weight basis theweightof the fabric, heating the fabric in an atmosphere of steam for aperiod of time sufficient to disperse the motes and render thenon-fibrous content of the fabric water extractable and washing theheated fabric with an aqueous solution.

5. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous alkalinesolution of a hypochlorite for a period of time sufficient tosubstantially impregnate the fabric with solution, removing theimpregnated fabric from solution, reducing the solution content of theimpregnated fabric to between 50 and 100 percent by weight basis theweight of the fabric, heating the impregnated fabric in an atmosphere ofsteam at temperatures between 180 and 500 F. for at least 15 minutes andwashing the heated fabric with an aqueous solution.

6. In the preparation of a sized cotton farbric for bleaching, the stepscomprising introducing the sized fabric into an aqueous alkalinesolution of a hypochlorite, said solution containing between 0.3 toabout 5 grams active chlorine per liter of solution and containingbetween 0.1 and 0.3 percent alkali metal silicate by weight of solution,maintaining the fabric in contact with the aqueous solution for a periodof time sufficient to impregnate substantially the fabric with thesolution, removing the impregnated fabric from the solution, reducingthe solution content of the fabric to between about 50 and percent byweight basis the weight of the fabric, heating the fabric in anatmosphere of steam at a temperature between about F. to about 500 F.for at least 15 minutes and washing the heated fabric with an aqueoussolution.

7. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous solution ofalkaline metal hydroxide and a hypochlorite for a period of timesufficient to substantially impregnate the fabric with solution,removing the impregnated fabric from the solution, heating theimpregnated fabric at elevated temperature for a period of timesufficient to disperse the motes and render the non-fibrous content ofthe fabric water extractable and washing the heated fabric with anaqueous solution.

8. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous solution of analkaline metal hydroxide and a hypochlorite, said solution containingbetween 0.1 and 3 percent alkali metal silicate by weight of thesolution and containing between about 0.3 to about 5 grams of activechlorine per liter of solution, maintaining the fabric in contact withthe aqueous alkali metal hydroxide solution until it is substantiallyimpregnated with the solution, removing the impregnated fabric from thesolution, heating the impregnated fabric at elevated temperature for aperiod of time sufficient to disperse the motes and render thenon-fibrous content of the fabric water extractable and washing theheated fabric with an aqueous solution.

9. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous solution of analkali metal hydroxide and a hypochlorite for a period of timesufficient to substantially impregnate the fabric with the solution,removing the impregnated fabric, reducing the solution content of thefabric to between about 50 to 150 percent by weight basis the weight ofthe fabric, heating the fabric in an atmosphere of steam for a period oftime suflicient to disperse the motes and render the non-fibrous contentof the fabric water extractable and washing the heated fabric with anaqueous solution.

10. In the preparation of a sized cotton fabric for bleaching the stepscomprising introducing the fabric into an aqueous solution of an alkalimetal hydroxide and a hypochlorite, said solution having between 0.3 toabout 5 grams of active chlorine per liter of solution and containingbetween 0.1 and 3 percent alkali silicate by weight of solution,maintaining the fabric in contact with the aqueous solution for a periodof time suflicient to substantially impregnate the fabric with solution,removing the impregnated fabric from the solution, reducing the solutioncontent of the fabric to between about 50 to 150 percent by weight basisthe weight of the fabric, heating the fabric in an atmosphere of steamfor a period of time sufficient to disperse the motes and render thenon-fibrous content of the fabric water extractable and "washing theheated fabric with an aqueous solution.

11. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous solution of analkali metal hydroxide and a hypochlorite for a period of timesufficient to substantially impregnate the fabric with solution,removing the impregnated fabric from solution, reducing the solutioncontent of the impregnated fabric to be between 50 and 150 percent byweight basis the weight of the fabric, heating the impregnated fabric inan atmosphere of steam at temperatures between 180 F. and

1 1 500 F. for at least 15 minutes and washing the heated fabric with anaqueous solution.

12. In the preparation of a sized cotton fabric for bleaching, the stepscomprising introducing the sized fabric into an aqueous solution of analkali metal hydroxide and a hypochlorite, said solution containingbetween 0.3 to about grams active chlorine per liter of solution andcontaining between 0.1 and 3 percent alkali metal silicate by weight ofsolution, maintaining the fabric in contact with the aqueous solutionfor a period of time suflicient to impregnate substantially the fabricwith the solution, removing the impregnated fabric from the solution,reducing the solution content of the fabric to between about 50 and 150percent by weight basis the weight of the fabric, heating the fabric inan atmosphere of steam at a temperature between about 180 to about 500F. for at least 15 minutes and Washing the heated fabric with an aqueoussolution.

13. In the bleaching of a sized cotton fabric, the steps comprisingintroducing sized fabric into an aqueous solution of an alkali metalhydroxide and a hypochlorite for a period of time suflicient toimpregnate substantially the fabric with solution, removing theimpregnated fabric from the solution and heating the impregnated fabricat elevated temperatures for a period of time sufficient to disperse themotes and render the non-fibrous content of the fabric waterextractable, introducing the heated fabric into an aqueous washsolution, removing the fabric from said wash solution and introducingthe fabric into an aqueous solution of hydrogen peroxide for a period oftime sufficient to impregnate substantially the fabric with solution.

14. In the bleaching of a sized cotton fabric, the steps comprisingintroducing the sized fabric into an aqueous solution of an alkali metalhydroxide and a hypochlorite for a period of time sufiicient toimpregnate substantially the fabric with solution, removing theimpregnated fabric from the solution and heating the impregnated fabricat elevated temperatures for a period of time sufficient to disperse themotes and render the non-fibrous content of the fabric waterextractable, washing the heated fabric with an aqueous solution,introducing the fabric into an aqueous solution of hydrogen peroxide fora period of time suflicient to substantially impregnate the fabric withsolution, heating the impregnated fabric at elevated temperatures for aperiod of time suflicient to bleach substantially the impregnatedfabric.

15. In the bleaching of a sized cotton fabric, the steps comprisingintroducing the sized fabric into an aqueous solution of an alkali metalhydroxide and a hypochlorite for a period time sufiicient tosubstantially impregnate the fabric with solution, removing theimpregnated fabric, reducing the solution content of the fabric tobetween about 50 and 150 percent by weight basis the weight of thefabric, heating the fabric in an atmosphere of steam for a period oftime suflicient to disperse the motes and render the non-fibrous contentof the fabric water extractable, washing the heated fabric with anaqueous solution, introducing the washed fabric into an aqueous solutionof hydrogen peroxide for a period of time to impregnate substantiallythe fabric with solution,'reducing the solution content of the fabric tobetween 50 and 150 percent by weight basis the weight of the fabric andheating the fabric in an atmosphere of steam for a period of timesulficient to bleach substantially the impregnated fabric. I

16. In the bleaching of a sized cotton fabric, the steps comprisingintroducing the fabric into an aqueous solution of alkali metalhydroxide and a hypochlorite, said solution having between 0.3 to about5 grams active chlorine per liter of solution and containing between 0.1and 3 percent alkali metal silicate by weight of solution,

maintaining the fabric in contact with the aqueous solution for a periodof time sufiicient to substantially impregnate the fabric with solution,removing the impregnated fabric from the solution, reducing the solutioncontent of the fabric to between about 50 and percent by weight basisthe weight of the fabric, heating the fabric in an atmosphere of steamfor a period of time sufficient to disperse the motes and render thenon-fibrous content of the fabric water extractable, washing the heatedfabric with an aqueous solution, introducing the washed fabric into anaqueous solution of hydrogen peroxide containing between 0.1 and 1percent hydrogen peroxide by weight, maintaining the fabric in solutionfor a period of time sufl'icient to impregnate substantially the fabricwith a solution, reducing the solution content of the fabric to between50 and 150 percent by weight basis the weight of the fabric and heatingthe impregnated fabric at elevated temperature for a period of timesutficient to bleach substantially the impregnated fabric.

17. In the bleaching of a sized cotton fabric, the steps comprisingintroducing the sized fabric into an aqueous solution of an alkali metalhydroxide and a hypochlorite for a period of time sufiicient tosubstantially impregnate the fabric with solution, removing theimpregnated fabric from solution, reducing the solution content of theimpregnated fabric to between 50 and 150 percent by weight basis theweight of the fabric, heating the impregnated fabric in an atmosphere ofsteam at temperatures between 212 and 500 F. for at least 15 minutes,washing the heated fabric with an aqueous solution, introducing thewashed fabric into an aqueous solution of hydrogen peroxide for a periodof time suflicient to impregnate substantially the fabric with solution,said hydrogen peroxide solution containing between 0.1 and 1 percenthydrogen peroxide by weight of solution, reducing the solution contentof the fabric to between 50 and 150 percent by weight basis the weightof the fabric and heating the impregnated fabric in an atmosphere ofsteam at temperatures between 180 and 500 F. for at least 15 minutes.

18. In the bleaching of a sized cotton fabric, the steps comprisingintroducing the sized fabric into an aqueous solution of an alkali metalhydroxide and a hypochlorite, said solution containing between 0.3 toabout 5 grams active chlorine per liter of solution, and containingbetween 0.1 and 3 percent alkali metal silicate by weight of solution,maintaining the fabric in contact with the aqueous solution for a periodof time sufiicient to impregnate substantially the fabric with solution,removing the impregnated fabric from the solution, reducing the solutioncontent of the fabric to between about 50 and 150 percent by weightbasis the weight of the fabric, heating the fabric in an atmosphere ofsteam at a temperature between about 212 to 500 F. for at least 15minutes, washing the heated fabric with an aqueous solution, introducingthe washed fabric into an aqueous solution of hydrogen peroxide for aperiod of time sufiicient to impregnate substantially the fabric withsolution, said aqueous hydrogen peroxide solution containing between 0.1and 1 percent hydrogen peroxide by weight of solution, reducing thesolution content of the fabric to between 50 and 150 percent by weightbasis the weight of the fabric and heating the impregnated fabric in anatmosuphere of steam at temperatures between about 180 to about 500 F.for at least 15 minutes.

References Cited in the file of this patent UNITED STATES PATENTS2,334,066 Campbell et a1. Nov. 9, 1943 2,839,353 Coleman June 17, 19582,868,615 Bell Jan. 13, 1959 2,903,327 Rogers Sept. 8, 1959 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,030,171April 17, 1962 Joseph Lindsay It is hereby certified that error appearsin the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column 1, line 12, for "bleacing" read bleaching column 2, line 38, for"filameburners" read flameburners column '7, in the footnote to Table 1,line 8, after "held" inse 2 column 9, line 66, for "100" read 150 line'71, for farbr'1c" read fabric column 11, line 50, after "period" insertof column 12, line 62, for "atmosuphere" read atmosphere Signed andsealed this 20th day of November 1962.

(SEAL) Attesl:

ERNEST w. SWIDER DAVID LADD Atlesting Officer Commissioner of Patents

1. IN THE PEPARATION OF A SIZED COTTON FABRIC FOR BLEACHING, THE STEPSCOMPRISING INTRODUCING THE SIZED FABRIC INTO AN AQUEOUS ALKALINESOLUTION OF A HYPOCHLORITE FOR A PERIOD OF TIME SUFFICIENT TOSUBSTANTIALLY IMPREGNATE THE FABRIC WITH SOLUTION, REMOVING THEIMPREGNATED FABRIC